The present invention relates to a power transmission control device, a power transmission device, a non-contact power transmission system, and an electronic instrument.
In recent years, non-contact power transmission (contactless power transmission) that utilizes electromagnetic induction to enable power transmission without metal-to-metal contact has attracted attention. As application examples of non-contact power transmission, charging a portable telephone, a household appliance (e.g., cordless telephone handset or watch), and the like has been proposed.
JP-A-2006-60909 discloses a non-contact power transmission device using a primary coil and a secondary coil, for example.
A non-contact power transmission device is strongly desired to consume only a small amount of power in order to increase the life of a battery of an electronic instrument, for example. Therefore, it is important to suppress unnecessary power transmission from a primary-side instrument (power-transmission-side instrument) to a secondary-side instrument (power-reception-side instrument) as much as possible.
A non-contact power transmission device is desired to achieve a high degree of safety and reliability. For example, when power is transmitted to a non-standard secondary-side instrument, the instrument may break down.
Even when power is transmitted to a secondary-side instrument that conforms to a specific standard, power transmission must be stopped when the power transmission environment is inappropriate.
For example, when power is transmitted in a state in which a metal foreign object is present, abnormal heat generation may occur. In this case, power transmission must be stopped. A metal foreign object may be small or medium-sized, or may be large (e.g., a thin sheet which is present over the entire area between a primary-side instrument and a secondary-side instrument). Therefore, it is desirable to take appropriate safety measures irrespective of the size or type of foreign object.
A non-contact power transmission device is also desired to improve convenience to the user.
Moreover it is important to reduce the size and the cost of a non-contact power transmission device by reducing the number of parts.